Proxmox configuration with Dual-Stack Networking, IPv4 NAT and Public IPv6 via Hurricane Electric Tunnel Broker

proxmox-natipv4-pubhetunnel.conf

auto lo
iface lo inet loopback

auto he-ipv6
iface he-ipv6 inet6 tunnel
        address xxxx:xxx:xx:xxx::2/128
        gateway xxxx:xxx:xx:xxx::1
        mode sit
        endpoint xxx.xxx.xxx.xxx
        local xxx.xxx.xxx.xxx
        ttl 255

auto vmbr0
iface vmbr0 inet static
        address YOUR_V4_IP/32
        gateway YOUR_V4_GATEWAY
        bridge-ports eno1
        bridge-stp off
        bridge-fd 0

auto vmbr1
iface vmbr1 inet static
        address 10.10.10.1/24
        bridge-ports none
        bridge-stp off
        bridge-fd 0
        post-up echo 1 > /proc/sys/net/ipv4/ip_forward
        post-up iptables -t nat -A POSTROUTING -s '10.10.10.0/24' -o vmbr0 -j MASQUERADE
        post-down iptables -t nat -D POSTROUTING -s '10.10.10.0/24' -o vmbr0 -j MASQUERADE

iface vmbr1 inet6 static
        address xxxx:xxx:xx:xxx:xxx::1/64
        up ip -6 route add xxxx:xxx:xx:xxx:xxxx::/64 dev vmbr1